package com.cqrcb.cloud.utils;

import lombok.extern.slf4j.Slf4j;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.HashSet;

/**
 * Twitter的分布式自增ID雪花算法snowflake (Java版)
 *
 * @author yangxueyong
 * @date 2021/06/01
 */
//@Slf4j
public class SnowFlakeUtils {

    private static SnowFlakeUtils snowFlake = new SnowFlakeUtils((int) (Math.random() * 5 + 1), (int) (Math.random() * 5 + 1));

    /**
     * 起始的时间戳
     */
    private final static long START_STMP = 1480166465631L;

    /**
     * 每一部分占用的位数
     */
    private final static long SEQUENCE_BIT = 12; //序列号占用的位数
    private final static long MACHINE_BIT = 5;   //机器标识占用的位数
    private final static long DATACENTER_BIT = 5;//数据中心占用的位数

    /**
     * 每一部分的最大值
     */
    private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);
    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);

    /**
     * 每一部分向左的位移
     */
    private final static long MACHINE_LEFT = SEQUENCE_BIT;
    private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
    private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;

    //数据中心
    private long datacenterId;

    //机器标识
    private long machineId;

    //序列号
    private long sequence = 0L;

    //上一次时间戳
    private long lastStmp = -1L;

    public SnowFlakeUtils(long datacenterId, long machineId) {
        if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
            throw new IllegalArgumentException("datacenterId can't be greater than MAX_DATACENTER_NUM or less than 0");
        }
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
        }
        this.datacenterId = datacenterId;
        this.machineId = machineId;
    }


    /**
     * 获取id
     */
    public static long getId(){
        return snowFlake.nextId();
    }

    /**
     * 产生下一个ID
     *
     * @return
     */
    private synchronized long nextId() {
        long currStmp = getNewstmp();
        if (currStmp < lastStmp) {
            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
        }

        if (currStmp == lastStmp) {
            //相同毫秒内，序列号自增
            sequence = (sequence + 1) & MAX_SEQUENCE;
            //同一毫秒的序列数已经达到最大
            if (sequence == 0L) {
                currStmp = getNextMill();
            }
        } else {
            //不同毫秒内，序列号置为0
            sequence = 0L;
        }

        lastStmp = currStmp;

        return (currStmp - START_STMP) << TIMESTMP_LEFT //时间戳部分
                | datacenterId << DATACENTER_LEFT       //数据中心部分
                | machineId << MACHINE_LEFT             //机器标识部分
                | sequence;                             //序列号部分
    }

    private long getNextMill() {
        long mill = getNewstmp();
        while (mill <= lastStmp) {
            mill = getNewstmp();
        }
        return mill;
    }

    private long getNewstmp() {
        return System.currentTimeMillis();
    }



    public static void main(String[] args) {
//        SnowFlakeUtils snowFlake = new SnowFlakeUtils(2, 3);
//        try {
//            InetAddress address = InetAddress.getLocalHost();
//            String hostAddress = address.getHostAddress();
//            System.out.println(hostAddress.substring(hostAddress.lastIndexOf(".")+1));
//        } catch (UnknownHostException e) {
//            e.printStackTrace();
//        }


        HashSet<Object> objects = new HashSet<>();
        long start = System.currentTimeMillis();
        for (int i = 0; i < 1000000; i++) {
            System.out.println(objects.add(SnowFlakeUtils.getId()));
        }
        System.out.println("objects->" + objects.size());
        System.out.println(System.currentTimeMillis() - start);

    }
}
